U.S. patent application number 13/233438 was filed with the patent office on 2013-03-21 for sorbent substrates for co2 capture and methods for forming the same.
The applicant listed for this patent is Karen Jo Knapp, Steven Bolaji Ogunwumi, Elizabeth Margaret Wheeler, John Forrest Wight, JR., James William Zimmermann. Invention is credited to Karen Jo Knapp, Steven Bolaji Ogunwumi, Elizabeth Margaret Wheeler, John Forrest Wight, JR., James William Zimmermann.
Application Number | 20130068101 13/233438 |
Document ID | / |
Family ID | 46889454 |
Filed Date | 2013-03-21 |
United States Patent
Application |
20130068101 |
Kind Code |
A1 |
Knapp; Karen Jo ; et
al. |
March 21, 2013 |
Sorbent Substrates for CO2 Capture and Methods for Forming the
Same
Abstract
Sorbent substrates for CO.sub.2 capture and methods for forming
the same are disclosed. In one embodiment, a method for forming a
sorbent substrate for CO.sub.2 capture may include forming a
plurality of matrix rods from a sorbent material and forming a
plurality of channel rods from a support material. The plurality of
matrix rods may then be co-extruded with the plurality of channel
rods to form a plurality of sorbent filaments comprising a matrix
of the sorbent material in which channels of support material are
positioned such that the channels extend in an axial direction of
each of the plurality of sorbent filaments. The plurality of
sorbent filaments may then be stacked to form a filament assembly
in which the plurality of sorbent filaments are axially aligned.
Thereafter, the plurality of sorbent filaments of the filament
assembly may be bonded to one another to form the sorbent
substrate.
Inventors: |
Knapp; Karen Jo; (Addison,
NY) ; Ogunwumi; Steven Bolaji; (Painted Post, NY)
; Wheeler; Elizabeth Margaret; (Lindley, NY) ;
Wight, JR.; John Forrest; (Corning, NY) ; Zimmermann;
James William; (Corning, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Knapp; Karen Jo
Ogunwumi; Steven Bolaji
Wheeler; Elizabeth Margaret
Wight, JR.; John Forrest
Zimmermann; James William |
Addison
Painted Post
Lindley
Corning
Corning |
NY
NY
NY
NY
NY |
US
US
US
US
US |
|
|
Family ID: |
46889454 |
Appl. No.: |
13/233438 |
Filed: |
September 15, 2011 |
Current U.S.
Class: |
96/108 ;
156/244.11 |
Current CPC
Class: |
B29C 48/06 20190201;
B29C 48/11 20190201; B01J 20/28045 20130101; B01J 20/28054
20130101; B01J 20/3078 20130101; B01J 20/305 20130101; B29C 48/156
20190201; B01D 2253/20 20130101; B01D 2253/25 20130101; B01J
20/3293 20130101; B29C 48/05 20190201; B29C 48/34 20190201; B29C
48/16 20190201; Y02P 70/10 20151101; B01D 2253/108 20130101; B01J
20/3035 20130101; B01D 2253/34 20130101; B01D 2257/504 20130101;
B01D 2253/204 20130101; B29C 48/345 20190201; B01D 2253/311
20130101; B01D 53/0407 20130101; B01D 2253/10 20130101; B01J
20/3057 20130101; B01J 20/165 20130101; B01J 20/3007 20130101; Y02C
20/40 20200801 |
Class at
Publication: |
96/108 ;
156/244.11 |
International
Class: |
B01D 53/02 20060101
B01D053/02; B32B 38/10 20060101 B32B038/10; B32B 37/14 20060101
B32B037/14; B01D 53/62 20060101 B01D053/62; B29C 47/06 20060101
B29C047/06 |
Claims
1. A method for forming a sorbent substrate for CO.sub.2 capture,
the method comprising: forming a plurality of matrix rods from a
sorbent material for adsorbing CO.sub.2 from a gas stream; forming
a plurality of channel rods from a support material; co-extruding
the plurality of matrix rods with the plurality of channel rods to
form a plurality of sorbent filaments comprising a matrix of the
sorbent material comprising channels of support material, the
channels of support material extending in an axial direction of
each of the plurality of sorbent filaments; stacking the plurality
of sorbent filaments to form a filament assembly, wherein the
plurality of sorbent filaments are axially aligned in the filament
assembly; and bonding the plurality of sorbent filaments of the
filament assembly to one another to form the sorbent substrate.
2. The method of claim 1, wherein: the support material is a
fugitive material; and the method further comprises removing the
fugitive material from the plurality of sorbent filaments thereby
forming through-channels in the plurality of sorbent filaments.
3. The method of claim 1, further comprising coating the plurality
of sorbent filaments with a binding material prior to stacking the
plurality of sorbent filaments to form the filament assembly.
4. The method of claim 1, further comprising radially compacting
the filament assembly.
5. The method of claim 1, wherein the plurality of sorbent
filaments are bonded to one another by heating the filament
assembly.
6. The method of claim 1, wherein the matrix of the sorbent
material has a first porosity P1% such that
20%.ltoreq.P1%.ltoreq.70%.
7. The method of claim 1, wherein the sorbent substrate has a
voidage V such that 25%.ltoreq.V.ltoreq.75%.
8. The method of claim 1, further comprising stacking one or more
conduits with the plurality of sorbent filaments to form the
filament assembly.
9. The method of claim 1, further comprising drying the filament
assembly prior to bonding the plurality of sorbent filaments to one
another.
10. A method for forming a sorbent substrate for CO.sub.2 capture,
the method comprising: forming a plasticized batch of matrix
material comprising a sorbent material for adsorbing CO.sub.2 from
a process gas stream; forming a plasticized batch of fugitive
material; co-extruding the plasticized batch of matrix material
with the plasticized batch of fugitive material to form a plurality
of sorbent filaments comprising a matrix of the sorbent material
having channels of fugitive material extending in an axial
direction of each of the plurality of sorbent filaments; stacking
the plurality of sorbent filaments to form a filament assembly,
wherein the plurality of sorbent filaments are axially aligned in
the filament assembly; compressing the filament assembly; removing
the fugitive material from the filament assembly to form a
plurality of through-channels in each of the plurality of sorbent
filaments; and heating the filament assembly to bond the plurality
of sorbent filaments to one another to form the sorbent
substrate.
11. The method of claim 10, further comprising coating the
plurality of sorbent filaments with a binding material prior to
stacking the plurality of sorbent filaments to form the filament
assembly.
12. The method of claim 10, further comprising drying the filament
assembly prior to bonding the plurality of sorbent filaments.
13. The method of claim 10, further comprising positioning at least
one conduit amongst the plurality of sorbent filaments as the
plurality of sorbent filaments are stacked, wherein the at least
one conduit is formed from a material other than the sorbent
material.
14. The method of claim 10, wherein the plasticized batch of matrix
material comprises: from about 30 wt. % to about 75 wt. % of
sorbent material; from about 20 wt. % to about 40 wt. % of
inorganic binder; and from about 1 wt. % to about 10 wt. % organic
binder.
15. The method of claim 10, wherein each of the plurality of
through-channels has a diameter d such that 20
.mu.m.ltoreq.d.ltoreq.2000 .mu.m.
16. The method of claim 10, wherein the sorbent substrate has a
voidage V such that 25%.ltoreq.V.ltoreq.75%.
17. A sorbent substrate for CO.sub.2 capture, the sorbent substrate
comprising: a plurality of sorbent filaments, each sorbent filament
of the plurality of sorbent filaments comprising a matrix of
sorbent material in which a plurality of through-channels are
formed such that the plurality of through-channels extend through
the matrix of sorbent material from a first end of each sorbent
filament to a second end of each sorbent filament in an axial
direction of each sorbent filament, wherein: the sorbent material
is capable of adsorbing CO.sub.2 from a gas stream; the plurality
of sorbent filaments are axially aligned with one another such that
the plurality of through-channels of the plurality of sorbent
filaments are substantially parallel with one another; and each
sorbent filament of the plurality of sorbent filaments is bonded to
at least one other sorbent filament.
18. The sorbent substrate of claim 17, further comprising at least
one conduit axially aligned with the plurality of sorbent
filaments, wherein the at least one conduit is formed from a
material other than the sorbent material.
19. The sorbent substrate of claim 17, wherein the sorbent
substrate has a porosity P1% such that
20%.ltoreq.P1%.ltoreq.70%.
20. The sorbent substrate of claim 17, wherein the sorbent
substrate has a voidage V such that 25%.ltoreq.V.ltoreq.75%.
Description
BACKGROUND
[0001] 1. Field
[0002] The present specification generally relates to substrates
for capturing CO.sub.2 from a process gas stream and, more
specifically, to sorbent substrates for capturing CO.sub.2 from a
process gas stream which are formed from co-extruded sorbent
filaments comprising a plurality of through-channels and methods
for making the same.
[0003] 2. Technical Background
[0004] CO.sub.2 is a greenhouse gas that has been linked to global
warming CO.sub.2 is a bi-product of various industrial processes
such as, for example, coal-fired power plants, purification of
natural gas, oil recovery systems and the like. From an
environmental perspective, carbon trading and future regulations of
carbon emissions from flue gasses and other CO.sub.2 point sources
are economic drivers for improving the efficiency of CO.sub.2
capture technologies.
[0005] Various technologies are currently being used and/or
developed to improve the capture of CO.sub.2 from process gas
streams. Such technologies include, for example, the liquid amine
(MEA or KS-1) process, the chilled ammonia process and gas
membranes. While each of these technologies is effective for
removing CO.sub.2 from a process gas stream, each technology also
has drawbacks. For example, the amine process has associated
reactor corrosion issues, high capital costs and is considered to
be very energy intensive to operate. The chilled ammonia process is
still in its early phases of development and the commercial
feasibility of the process is not yet known. Some possible
challenges with the chilled ammonia process include ammonia
volatility and the potential contamination of the ammonia from
gaseous contaminants such as SO.sub.x and NO.sub.x. Various gas
membrane technologies are currently employed for the removal of
CO.sub.2 from process gas streams. However, processes utilizing gas
membrane technologies require multiple stages and/or recycling in
order to achieve the desired amount of CO.sub.2 separation. These
multiple stages and/or recycling add significant complexity to the
CO.sub.2 recovery process as well as increase the energy
consumption and cost associated with the process. Gas membrane
technologies also typically require high pressures and associated
space constraint which makes use of the technology difficult in
installations with limited space such as offshore platforms.
[0006] Accordingly, a need exists for alternative methods and
apparatuses which may be used to recover CO.sub.2 from process gas
streams.
SUMMARY
[0007] According to various embodiments, a method for forming a
sorbent substrate for CO.sub.2 capture may include forming a
plurality of matrix rods from a sorbent material for adsorbing
CO.sub.2 from a gas stream and forming a plurality of channel rods
from a support material. The plurality of matrix rods may then be
co-extruded with the plurality of channel rods to form a plurality
of sorbent filaments comprising a matrix of the sorbent material in
which channels of support material are positioned such that the
channels of support material extend in an axial direction of each
of the plurality of sorbent filaments. The plurality of sorbent
filaments may then be stacked to form a filament assembly in which
the plurality of sorbent filaments are axially aligned. Thereafter,
the plurality of sorbent filaments of the filament assembly may be
bonded to one another to form the sorbent substrate.
[0008] According to further embodiments, a method for forming a
sorbent substrate for CO.sub.2 capture may include forming a
plasticized batch of matrix material comprising a sorbent material
for adsorbing CO.sub.2 from a gas stream and forming a plasticized
batch of fugitive material. The plasticized batch of matrix
material may then be co-extruded with the plasticized batch of
fugitive material to form a plurality of sorbent filaments
comprising a matrix of the sorbent material having channels of
fugitive material extending in an axial direction of each of the
plurality of sorbent filaments. The plurality of sorbent filaments
may be stacked to form a filament assembly such that the plurality
of sorbent filaments are axially aligned in the filament assembly.
The filament assembly may be radially compacted. Thereafter, the
fugitive material may be removed from the filament assembly to form
a plurality of through-channels in each of the plurality of sorbent
filaments. The filament assembly may be heated to bond the
plurality of sorbent filaments to one another to form the sorbent
substrate.
[0009] According to still further embodiments, a sorbent substrate
for CO.sub.2 capture may include a plurality of sorbent filaments.
Each sorbent filament of the plurality of sorbent filaments may
include a matrix of sorbent material in which a plurality of
through-channels are formed such that the through-channels extend
through the matrix of sorbent material from a first end of each
sorbent filament to a second end of each sorbent filament in an
axial direction of each sorbent filament. The sorbent material may
be capable of adsorbing CO.sub.2 from a gas stream. The plurality
of sorbent filaments may be axially aligned with one another such
that the plurality of through-channels of the plurality of sorbent
filament are substantially parallel with one another. Each sorbent
filament of the plurality of sorbent filaments may be bonded to at
least one other sorbent filament.
[0010] Additional features and advantages of the embodiments
described herein will be set forth in the detailed description
which follows, and in part will be readily apparent to those
skilled in the art from that description or recognized by
practicing the embodiments described herein, including the detailed
description which follows, the claims, as well as the appended
drawings.
[0011] It is to be understood that both the foregoing general
description and the following detailed description describe various
embodiments and are intended to provide an overview or framework
for understanding the nature and character of the claimed subject
matter. The accompanying drawings are included to provide a further
understanding of the various embodiments, and are incorporated into
and constitute a part of this specification. The drawings
illustrate the various embodiments described herein, and together
with the description serve to explain the principles and operations
of the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 schematically depicts a portion of a sorbent
substrate for CO.sub.2 capture in which the substrate comprises a
plurality of sorbent filaments bonded together to form the
substrate, according to one or more embodiments shown and described
herein;
[0013] FIG. 2 schematically depicts a portion of another embodiment
of a sorbent substrate for CO.sub.2 capture in which the substrate
comprises a plurality of sorbent filaments bonded together to form
the substrate according to one or more embodiments shown and
described herein;
[0014] FIG. 3 schematically depicts an extrusion die for forming a
sorbent filament having through-channels according to one or more
embodiments shown and described herein;
[0015] FIGS. 4A-4C schematically depict sorbent filaments with
different cross sectional shapes according to one or more
embodiments shown and described herein;
[0016] FIG. 5 schematically depicts a filament assembly of a
sorbent substrate being radially compacted according to one or more
embodiments shown and described herein;
[0017] FIG. 6 schematically depicts an apparatus for removing
CO.sub.2 from a fluid stream according to one or more embodiments
shown and described herein; and
[0018] FIG. 7 schematically depicts an alternate embodiment of an
apparatus for removing CO.sub.2 from a fluid stream according to
one or more embodiments shown and described herein.
DETAILED DESCRIPTION
[0019] Reference will now be made in detail to embodiments of
sorbent substrates for capturing CO.sub.2 from a process gas stream
and methods for forming the same, examples of which are illustrated
in the accompanying drawings. Whenever possible, the same reference
numerals will be used throughout the drawings to refer to the same
or like parts. One embodiment of a sorbent substrate for capturing
CO.sub.2 from a process gas stream is schematically depicted in
FIG. 1. The sorbent substrate generally includes a plurality of
sorbent filaments which are axially aligned and bonded together.
Each of the sorbent filaments generally comprises a matrix of
sorbent material for capturing CO.sub.2 from a process gas stream.
A plurality of through-channels are formed in the matrix of sorbent
material utilizing a co-extrusion process. The sorbent substrates
and methods for forming the sorbent substrates will be described in
more detail herein with specific reference to the appended
drawings.
[0020] Referring now to FIG. 1, one embodiment of a sorbent
substrate 100 is schematically depicted. The sorbent substrate 100
may be used to capture CO.sub.2 from a process gas stream. The
sorbent substrate 100 is constructed from a plurality of individual
sorbent filaments 102 which are stacked and bonded together. In the
embodiment of the sorbent substrate 100 depicted in FIG. 1, the
sorbent filaments 102 are square in cross section. However, it
should be understood that, in other embodiments, the sorbent
filaments 102 may have other cross sectional shapes including,
without limitation, circular, rectangular, hexagonal, triangular,
or the like. For example, FIG. 2 schematically depicts a sorbent
substrate 100 which is circular in cross section and which is
formed from a plurality of individual sorbent filaments 102 which
are also circular in cross section.
[0021] Referring now to FIGS. 1 and 2, the sorbent filaments 102 of
the sorbent substrate 100 generally comprise a matrix of sorbent
material 106 in which a plurality of through-channels 104 are
formed. The matrix of sorbent material 106 is formed from a sorbent
material suitable for adsorbing CO.sub.2 from a process gas stream
and may include, without limitation, molecular sieve materials
having framework structures such as MFI, MOR, ISV, ITE, CHA, DDR,
FAU, and/or LTA framework structures and similar materials.
Exemplary materials include, without limitation, ZSM5 zeolite which
has an MFI framework structure, and Mordenite which has an MOR
framework structure. The sorbent materials may also include
sorbents based on activated carbon or carbon molecular sieve
materials. Alternatively, the sorbent material may be selected from
a metallic organic framework (MOF) family such as MOF-5, MOF-177,
MOF-505, MOF-74 or zeolitic imidazole framework structures (ZIFs)
including, without limitation, ZIF-68, ZIF-69, ZIF-7, ZIF-9, ZIF-11
and ZIF-90. Suitable sorbent materials may also include any of the
aforementioned materials functionalized with an amine or amino
group to further enhance the adsorption capacity of the material.
Moreover, it should be understood that the sorbent material
utilized in the sorbent substrate may comprise various combinations
of the aforementioned materials.
[0022] In the embodiments of the sorbent substrate 100 described
herein, the matrix of sorbent material 106 from which each sorbent
filament 102 is formed generally has an open, interconnected
porosity P1% which permits a process gas stream to permeate and
diffuse through the sorbent substrate 100. For example, in some
embodiments, the porosity P1% of the sorbent filaments is such that
20%.ltoreq.P1%.ltoreq.70%. In some other embodiments, the porosity
P1% is such that 25%.ltoreq.P1%.ltoreq.40. In general, the sorbent
filaments and the sorbent substrate are formed with an open
porosity which enables a process gas stream containing CO.sub.2 to
diffuse through the substrate while still permitting intimate
contact between the process gas stream and the matrix of sorbent
material to facilitate adsorption of the CO.sub.2 by the matrix of
sorbent material.
[0023] Still referring to FIGS. 1 and 2, each of the sorbent
filaments 102 of the sorbent substrate 100 are axially aligned with
one another. Moreover, the through-channels 104 generally extend
through the matrix of sorbent material 106 in an axial direction of
the sorbent filament 102 between a first end and a second end.
Accordingly, the plurality of through-channels 104 of each sorbent
filament 102 are substantially parallel with the plurality of
through-channels 104 of each adjacent sorbent filament.
[0024] The minimum diameter of the through channels is dependent on
the particle size of the sorbent material used in the matrix
material. In general, the minimum diameter of the channels is
3.times. the particle diameter of the sorbent material. In the
embodiments of the sorbent substrate 100 described herein, the
through-channels 104 of each sorbent filament 102 generally have a
diameter d such that 20 .mu.m.ltoreq.d.ltoreq.2000 .mu.m. In other
embodiments the through-channels 104 may be sized such that 50
.mu.m.ltoreq.d.ltoreq.1000 .mu.m. In still other embodiments, the
through-channels 104 of the sorbent filaments 102 may be sized such
that 75 .mu.m.ltoreq.d.ltoreq.500 .mu.m. Similar to the diameter d
of the through-channels, the minimum spacing between adjacent
channels is dependent on the particle size of the sorbent material
used in the matrix material. In general, the minimum spacing
attainable is 3.times. the particle diameter of the sorbent
material. In the embodiments described herein, the density of the
through-channels may be in a range from about 1 channel per square
in (cpsi) (0.155 channels/cm.sup.2) up to 150,000 cpsi (23,255
channels/cm.sup.2).
[0025] As noted above, each sorbent filament 102 of the sorbent
substrate 100 is bonded to at least one other sorbent filament. For
example, in some embodiments described herein, each sorbent
filament 102 is coated with a binding material which binds adjacent
sorbent filaments together. In some embodiments, the binding
material may be an inorganic material such as alumina, silica,
clay, ceria, aluminum phosphate, glass frit, geopolymers or similar
inorganic binding materials which have relatively low melting
points. Alternatively, the binding material may be an organic
binding material such as, for example, phenolic resins.
[0026] While the sorbent substrate 100 has been described herein as
comprising a binding material which binds the sorbent filaments 102
together, in other embodiments the sorbent substrate 100 may be
formed without the use of a binding material. For example, in some
embodiments the matrix of sorbent material 106 of each sorbent
filament 102 may be utilized to bind the individual sorbent
filaments together. For example, as will be described in more
detail herein, the matrix of sorbent material 106 of each sorbent
filament 102 may contain one or more inorganic binders which binds
the sorbent material in each filament together. Accordingly, once
the individual sorbent filaments have been assembled into the
sorbent substrate, the binder in the sorbent material may be
activated, such as by heating or the like, to bind the individual
sorbent filaments together.
[0027] In some embodiments described herein, the through-channels
104 of the sorbent substrate may further comprise a second sorbent
material which is coated on the walls of the through-channels. The
second sorbent material may be a metal or metallic oxide material
which is suitable for adsorbing CO.sub.2 from a process gas stream.
Exemplary materials for the second sorbent material include,
without limitation, alkali carbonates such as potassium carbonate
and sodium carbonate. Exemplary sodium carbonates include Trona and
sodium bicarbonate.
[0028] Referring now to FIG. 2, in the some embodiments the sorbent
substrate 100 may optionally comprise one or more conduits 108
(four depicted in FIG. 2) positioned amongst the sorbent filaments
102. In the embodiment shown in FIG. 2, the conduits 108 are
generally axially aligned with the sorbent filaments 102. However,
it should be understood that, in other embodiments (not shown) the
conduits may be non-parallel with the sorbent filaments 102 and the
corresponding through channels 104. The conduits facilitate
directing a flow of cooling fluid, such as a liquid or gas, through
the sorbent substrate 100 to facilitate cooling the substrate 100
as CO.sub.2 is adsorbed into the matrix of sorbent material.
Specifically, the reaction between the CO.sub.2 in a process gas
stream and the sorbent material of the sorbent substrate 100 is
generally an exothermic reaction. The heat produced as a result of
the reaction generally builds up in the substrate 100 and, under
certain conditions, may limit the ability of the substrate to
adsorb additional CO.sub.2 from a process gas stream. However,
cooling fluid directed through the through-channels 104 and/or the
conduit 108 draws heat from the matrix of sorbent material and
carries the heat away from the sorbent substrate 100, thereby
cooling the substrate and improving the ability of the sorbent
substrate 100 to adsorb CO.sub.2. The conduits 108 provide for a
larger flow path than the through-channels 104 and, as such,
provide improved thermal management capabilities over the
through-channels alone.
[0029] In a similar manner, the conduits 108 may also be utilized
to direct a heating fluid, such as liquid or gas, through the
sorbent substrate 100 to facilitate release of CO.sub.2 adsorbed in
the matrix of sorbent materials. As noted above, when CO.sub.2 is
adsorbed into the sorbent material, heat is generated. However, if
heat is added to the sorbent material, CO.sub.2 is released and the
adsorption process is reversed. In some embodiments described
herein, heat may be added to the matrix of sorbent material 106 by
directing a flow of heating fluid through the through-channels
and/or conduits 108 which, in turn, heats the sorbent substrate 100
causing the release of adsorbed CO.sub.2 and the regeneration of
the sorbent material.
[0030] In the embodiments described herein, the conduits 108 may be
formed from a material other than the sorbent material. In some
embodiments, the conduits 108 are formed from a thermally
conductive metal, ceramic or polymeric material. For example, when
the conduits are formed from a metallic material, the conduits may
be formed from copper or a copper alloy, aluminum or an aluminum
alloy, stainless steel, copper-beryllium alloys and/or other
thermally conductive materials.
[0031] Referring now to FIGS. 1 and 2, the sorbent substrates
described herein generally have a voidage V, which is defined as
the percentage of open volume (i.e., pores, channels, conduits and
the like) within the total volume of the substrate. The sorbent
substrates described herein generally have a voidage of less than
about 82.5%. In some embodiments, the voidage may be such that
25%.ltoreq.V.ltoreq.75%. In other embodiments the voidage may be
such that 25%.ltoreq.V.ltoreq.70%. Maintaining the voidage in this
range improves the efficiency and activity of the substrate for
capturing CO.sub.2 from a process gas stream. In some embodiments
the voidage may be less than 70%.
[0032] Methods for forming the sorbent substrates will now be
described with specific reference to FIGS. 3-5.
[0033] As noted above, the sorbent substrates described herein
comprise a plurality of sorbent filaments which are stacked and
bonded together to form a substrate having through-channels of the
desired dimensions. The dimensions of the through-channels formed
in individual sorbent filaments are achieved by forming the
individual sorbent filaments by a co-extrusion process which
facilitates forming the through-channels and reducing the
through-channels and sorbent filaments to the desired
cross-sectional size without collapsing the through-channels.
[0034] The sorbent filaments of the sorbent substrate are formed by
first mixing a batch of plasticized matrix material. The batch of
plasticized matrix material comprises the sorbent material, an
organic binder, an inorganic binder, processing aids, and a liquid
vehicle. As noted hereinabove, the sorbent material comprises a
material suitable for adsorbing CO.sub.2 from a process gas stream
and may include, without limitation, molecular sieve materials
having framework structures such as MFI, MOR, ISV, ITE, CHA, DDR,
FAU, and/or LTA framework structures and similar materials.
Exemplary materials include, without limitation, ZSM5 zeolite which
has an MFI framework structure, and Mordenite which has an MOR
framework structure. The sorbent materials may also include
sorbents based on activated carbon or carbon molecular sieve
materials. Alternatively, the sorbent material may be selected from
a metallic organic framework (MOF) family such as MOF-5, MOF-177,
MOF-505, MOF-74 or zeolitic imidazole framework structures (ZIFs)
including, without limitation, ZIF-68, ZIF-69, ZIF-7, ZIF-9, ZIF-11
and ZIF-90. Suitable sorbent materials may also include any of the
aforementioned materials functionalized with an amine or amino
group to further enhance the adsorption capacity of the material.
Moreover, it should be understood that the sorbent material
utilized in the sorbent substrate may comprise various combinations
of the aforementioned materials.
[0035] The sorbent material is provided in a powder form. In some
embodiments the sorbent material has an average particle size in
the range from about 1 nm to about 1000 nm In other embodiments,
the sorbent material has an average particle size in the range from
about 5 nm to about 500 nm. In the embodiments described herein the
sorbent material is present in the batch of plasticized matrix
material in an amount from about 30 wt. % to about 75 wt. % by
weight of the batch. In other embodiments, the batch of plasticized
matrix material includes from about 40 wt. % to about 50 wt. % of
sorbent material by weight of the batch.
[0036] The organic binders included in the plasticized batch of
matrix material facilitate extruding the matrix material during
formation of the sorbent filaments. Suitable organic binders
include, without limitation, water soluble cellulose ether binders
such as methylcellulose, hydroxypropyl methylcellulose,
methylcellulose derivatives, hydroxyethyl acrylate,
polyvinylalcohol, and/or combinations thereof. Preferably, the
organic binder is present in the batch as a super addition in an
amount in the range of from 0.1 wt. % to about 10.0 wt. % by weight
of the sorbent material in the batch. In another embodiment, the
organic binder can be present in the composition as a super
addition in an amount in the range of from 2.0 wt. % to 8.0 wt. %
by weight of the sorbent material in the batch.
[0037] The inorganic binders included in the plasticized batch of
matrix material facilitate binding the sorbent material following
formation of the sorbent filaments by extrusion. In the embodiments
described herein, the inorganic binder may be a silicone binding
agent such as silicone resins and/or silicone emulsions. These
silicone materials can be provided as precursor materials such as,
for example, silicone resin or colloidal silica. In some
embodiments the inorganic binder is incorporated in the form of a
silicone resin or silicone emulsion. Suitable silicone resins
include, without limitation, aqueous emulsions of silicone such as
Wacker A G SILRES.RTM. M 50 E (an emulsion of a methyl silicone
resin with reported solids content of 52-55%) or Wacker A G
SILRES.RTM. M 97 E, both of which are available from Wacker-Chemie
GmbH of Munich, Germany. The inorganic binder is incorporated in
the batch mixture in an amount ranging from about 5 wt. % to about
50 wt. % by weight of the batch, preferably from about 20 wt. % to
about 40 wt. % by weight and, more preferably, from about 20 wt. %
to about 35 wt. % by weight of the batch.
[0038] The liquid vehicle acts as a solvent for the organic binders
and generally provides a flowable or paste-like consistency to the
plasticized batch composition of matrix material to facilitate
extrusion of the batch. In the embodiments described herein,
deionized water is utilized as the liquid vehicle. However, it
should be understood that other liquid vehicles exhibiting solvent
action with respect to the organic binders may also be used as an
alternative to water or in addition to water. The amount of the
liquid vehicle in the plasticized batch of matrix material may vary
depending on the desired rheology of the batch. In some
embodiments, the liquid vehicle is present in the batch as a super
addition in an amount from about 1.0 wt. % to 50 wt. % by weight of
the batch. In other embodiments, the liquid vehicle is present in
the batch as a super addition in an amount from 1.0 wt. % to 20 wt.
% by weight of the batch. Minimization of the liquid component in
the batch reduces undesired drying shrinkage and crack formation
during subsequent drying.
[0039] In addition to the sorbent material, liquid vehicle, organic
binders, and inorganic binders, the plasticized batch composition
may also include one or more optional forming or processing aids
such as, for example, a lubricant. Exemplary lubricants include
tall oil, sodium stearate, Durasyn 162 (polyphaolefin) or other
suitable lubricants and/or combinations thereof. The amount of
lubricant present in the plasticized batch mixture may be from
about 0.1 wt. % to about 10 wt. % by weight of the batch.
[0040] In the embodiments described herein, the plasticized batch
of matrix material is formed by first dry mixing the sorbent
material and the organic binder. The mixing may be performed
utilizing a three axis mixer such as a Turbula mixer. Thereafter,
the remaining components of the batch composition (i.e., the
inorganic binder, liquid vehicle, and processing aids) are added to
the dry mix of sorbent material and organic binder and mixed with a
muller to form an extrudable paste (i.e., the plasticized batch
composition of matrix material).
[0041] To form the sorbent filaments of the sorbent substrates
described herein, a plasticized batch of support material is also
formed in addition to the plasticized batch of matrix material. The
support material is utilized to form and retain the shape of the
through-channels in a co-extrusion process with the matrix
material. In the embodiments described herein, the plasticized
batch of support material generally includes the support material
and one or more processing aids such as lubricants or the like.
However, it should be understood that the plasticized batch of
support material may include other components (e.g., binders, a
liquid vehicle, pore formers and the like) depending on the type of
support material selected and the desired properties of the support
material following formation of the sorbent filaments.
[0042] In the embodiments described herein, the support material is
ultimately removed from the sorbent filaments and, as such, the
support material is a fugitive material. Accordingly, the support
material must be capable of being readily removed from the sorbent
filaments without damaging the sorbent filaments. In the
embodiments described herein, the support material may include heat
softenable materials such as natural or synthesized fatty acids,
polyalcohols and/or esthers, paraffins, natural or synthetic
hydrocarbon waxes, or synthesized thermoplastic polymeric
materials. In embodiments where the support material is a wax, the
wax may be microcrystalline wax or crystalline wax. For example,
suitable wax materials include, without limitation,
microcrystalline wax such as Ultraflex wax or Victory wax
manufactured by Bareco, Witco W-445 wax or Witco W-835 wax
manufactured by Chemtura. Alternatively, the support material may
be a material which sublimes upon heating including, without
limitation, sulfur or a similar material. The support material is
generally present in the plasticized batch of support material in
an amount greater than 75 wt. % by weight of the batch. For
example, the fugitive material may be present in an amount greater
than 80 wt. % or even greater than 90 wt. % by weight of the
batch.
[0043] Further, in embodiments where the support material is a
fugitive material such as wax, the batch of support material may
additionally include processing aids such as lubricants. Suitable
lubricants include, without limitation, tall oil, graphite, and/or
combinations thereof. These processing aids are generally present
in the batch composition in an amount which is less than 25 wt. %
of the batch. In some embodiments, the processing aids are present
in the batch in an amount which is less than 10 wt. % of the
batch.
[0044] In embodiments where the support material is a wax, the
plasticized batch of support material is formed by heating the wax
to form molten wax. Thereafter, the processing aids are added to
the wax and the batch is mixed and cooled to solidify the
batch.
[0045] As noted hereinabove, in some embodiments, the
through-channels 104 of the substrate may be coated with a second
sorbent material, such as a metal or metal oxide. Exemplary
materials include, without limitation, alkali carbonates such as
potassium carbonate and sodium carbonate. This second sorbent
material may be added to the plasticized batch of support material
such that, when the support material is removed from the sorbent
filaments, a portion of the second sorbent material remains on the
walls of the through-channels.
[0046] In one embodiment, following formation of the plasticized
batch of matrix material and formation of the plasticized batch of
matrix material, each batch of material is separately extruded into
rods prior to forming the sorbent filaments by co-extruding the
matrix material with the support material. For example, in one
embodiment, the plasticized batch of matrix material is extruded
into cylindrical matrix rods. Similarly, the plasticized batch of
support material may be co-extruded into cylindrical channel rods.
Separately extruding the plasticized batch of matrix material and
the plasticized batch of support material prior to forming the
sorbent filaments by co-extrusion improves the homogeneity of the
respective batch mixtures.
[0047] Referring now to FIG. 3, after the plasticized batch of
matrix material and the plasticized batch of support material have
been formed and optionally extruded into rods, the batch materials
are co-extruded to form sorbent filaments comprising a matrix of
sorbent material having channels containing support material. In
the embodiments described herein, the sorbent filaments are formed
using the co-extrusion die 120 schematically depicted in FIG. 3.
The co-extrusion die 120 generally comprises a first inlet 122 for
receiving the plasticized batch of support material or support rods
formed from the support material and a second inlet 124 for
receiving the plasticized batch of matrix material or matrix rods
formed from the matrix material. In the embodiments described
herein, the first inlet 122 and second inlet 124 may be coupled to
either ram-type extruders or screw-type extruders which deliver the
matrix material and support material to the co-extrusion die 120
under pressure. For example, in embodiments where the plasticized
batch of matrix material and the plasticized batch of support
material are separately extruded into rods prior to formation of
the sorbent filaments, ram-type extruders are utilized to deliver
the materials to respective inlets 122, 124. However, in
embodiments where the plasticized batch of matrix material and the
plasticized batch of support material are not separately extruded
into rods prior to formation of the sorbent filaments, either
screw-type extruders or ram-type extruders are utilized to deliver
the materials to respective inlets 122, 124.
[0048] A flow 150 of support material enters the co-extrusion die
120 at inlet 122 and flows into the inner chamber 126 of the
co-extrusion die 120 under pressure. Simultaneously, a flow 152 of
matrix material enters the co-extrusion die 120 at inlet 124 and
flows into outer chamber 128 under pressure. The inner chamber 126
and outer chamber 128 are separated by a wall which prevents the
flow 150 of support material from mixing with the flow 152 of
matrix material. The extrusion pressure applied to the flow 150 of
support material forces the support material through the nozzles
134 of forming die 130, thereby re-shaping the flow 150 of support
material into a plurality of individual rods which exit the forming
die 130 into forming chamber 136. At the same time, the extrusion
pressure applied to the flow 152 of matrix material forces the
matrix material around the nozzles 134 of the forming die 130 and
into the forming chamber 136. As the matrix material enters the
forming chamber 136, the matrix material is compressed around the
nozzles 134 of the forming die 130, thereby enveloping the rods of
support material exiting the nozzles 134 and forming a bi-component
extrudate comprising channels of support material in a matrix of
sorbent material.
[0049] Thereafter, continued extrusion pressure on both the flow
150 of support material and the flow 152 of matrix material forces
the bi-component extrudate into the conical reducing die 132 which
reduces the overall diameter of the bi-component extrudate as well
as the diameter of the rods of support material contained in the
bi-component extrudate, thereby forming a sorbent filament which
exits the reducing die 132 at outlet 135.
[0050] Referring now to FIGS. 4A-4C, exemplary sorbent filaments
formed using the co-extrusion die depicted in FIG. 3 are
schematically depicted. Specifically, FIG. 4A schematically depicts
one embodiment of a sorbent filament 102a having a square cross
section, FIG. 4B schematically depicts a second embodiment of a
sorbent filament 102b having a circular cross section, and FIG. 4C
schematically depicts a third embodiment of a sorbent filament 102c
having an octagonal cross section. Each of the sorbent filaments
comprises a matrix of sorbent material 106 in which a plurality of
through-channels 104 are formed, as described above. In the
embodiments of the sorbent filaments 102a, 102b, 102c depicted in
FIGS. 4A-4C, the through-channels 104 contain support material 110.
The cross sectional shape of the sorbent filaments is dictated by
the cross sectional shape of the reducing die 132 (FIG. 3).
Accordingly, it should be understood that sorbent filaments with
various cross sectional shapes may be formed by using reducing dies
having the desired cross sections.
[0051] Further, the dimensions of the sorbent filaments (i.e., the
maximum outer diameter D of the sorbent filament and the diameter d
of the through-channels) are also controlled by the geometry of the
reducing die utilized to form the sorbent filaments, the flow
behavior of the binders contained in the material, the maximum
pressure of the extruder(s) and the particle size of the sorbent
material. In some embodiments described herein, the maximum outer
diameter D of the sorbent filaments (i.e., the maximum distance
between two points on the perimeter of the filament) may be as
small as 21.times. the particle size of the sorbent material.
However, in other embodiments described herein, the sorbent
filaments have a maximum outer diameter D such that 1
mm.ltoreq.D.ltoreq.50 mm, while in other embodiments the maximum
outer diameter D of the sorbent filament is such that 2
mm.ltoreq.D.ltoreq.15 mm.
[0052] Moreover, it should be understood that the number and
diameter d of the through-channels 104 formed in each sorbent
filament is dependent on the number and size of the nozzles in the
forming die 130 (FIG. 3). For example, it is contemplated that as
many as 2200 through-channels having a diameter d in the order of
tens of microns may be formed in a sorbent filament having a
maximum diameter D of approximately 33 mm (i.e., a sorbent filament
with a 2.4 mm.times.2.4 mm square cross section).
[0053] In one embodiment, after the sorbent filaments are formed by
co-extruding the plasticized batch of matrix material with the
plasticized batch of sorbent material, the sorbent filaments may be
optionally coated with a binding material to facilitate binding the
individual sorbent filaments together in a subsequent stacking
step. The binding material may be an inorganic binding material
such as alumina, silica, clay, ceria, aluminum phosphate, glass
frit, geopolymers or similar inorganic binding materials which have
relatively low melting points. Alternatively, the binding material
may be an organic binding material such as, for example, phenolic
resins. The minimum thickness of the coating of binding material is
generally 3.times. the particle size of the binding material. In
one embodiment, the binding material comprises alumina having a
particle size of 70 .mu.m which is applied to the filaments in a
colloidal suspension such that each sorbent filament comprises an
alumina coating having a thickness of at least 210 .mu.m.
[0054] Referring now to FIG. 5, after the sorbent filaments 102
have been formed and optionally coated with a binding material, the
filaments are stacked and axially aligned in a segmented frame 139
to form a filament assembly. The segmented frame is shaped to
correspond to the desired shape of the resultant sorbent substrate.
For example, in the embodiment shown in FIG. 5, the sorbent
filaments 102 are stacked in a square segmented frame 139 to form a
filament assembly which may be used to produce a sorbent substrate
which has a square cross section as depicted in FIG. 1. However, it
should be understood that frames of different geometrical
configurations may be utilized. For example, in one embodiment the
frame may be cylindrical in shape and comprise a plurality of
semi-cylindrical segments. In the embodiment of the segmented frame
139 depicted in FIG. 5, the segmented frame 139 generally comprises
a first segment 140a, a second segment 140b, a third segment 140c
and a fourth segment 140d, each of which may be individually
positioned with respect to the sorbent filaments. In embodiments
where conduits are included in the sorbent substrate, the conduits
may be stacked in the segmented frame amongst the sorbent filaments
and axially aligned with the sorbent filaments.
[0055] Once the sorbent filaments and any conduits are stacked in
the segmented frame 139 and axially aligned, a radial compaction
force F is applied to each of the segments 140a, 140b, 140c, 140d
of the frame to compress the frame and shape the sorbent filaments
102 into a filament assembly having the desired shape. In
embodiments where the sorbent filaments are round or have a
geometrical configuration which produces interstitial spaces
between the sorbent filaments when the filaments are stacked, the
compaction force F applied to the segmented frame may be sufficient
to remove the interstitial spaces between the sorbent filaments
102. The compaction force F may be applied to the segmented frame
139 with mechanical clamps (not shown), such as band clamps or the
like such that the segmented frame 139 and the sorbent filaments
102 contained therein are isostatically compressed. Alternatively,
the compaction force may be applied to the segmented frame with one
or more hydraulic rams. The support material contained in the
through-channels of the sorbent filament prevents the
through-channels from collapsing during the compaction process. In
some embodiments, the filaments and the frame may be placed under
vacuum prior to and during application of the compaction force F to
improve knitting between adjacent sorbent filaments 102.
[0056] Thereafter, the filament assembly comprising the compacted
sorbent filaments is dried to remove water from the assembly. For
example, the filament assembly may be dried by placing the filament
assembly in an oven and heating the filament assembly to a drying
temperature T.sub.d and holding the assembly at this temperature
for a predetermined amount of time. In some embodiments, the drying
temperature T.sub.d may be in a range from about 90.degree. C. to
about 150.degree. C. In these embodiments the drying time may be
approximately twelve hours.
[0057] In some embodiments, the melting or sublimation temperature
of the support material positioned in the through-channels may be
within the drying temperature range. In these embodiments, the
support material may begin to melt and drain from the assembly
during drying. As such, the filament assembly may be positioned at
an angle during drying to facilitate draining the melted support
material from the filament assembly.
[0058] In other embodiments, the support material may have a
melting temperature which is greater than the drying temperature
T.sub.d. In these embodiments a separate step of heating the
filament assembly to a temperature in excess of the melting
temperature of the support material may be utilized to remove the
support material from the through-channels after the assembly has
been dried. In yet another embodiment, the support material may be
removed from the filament assembly during a separate bonding step.
In some embodiments, the dried assembly is placed under vacuum and
heated to a temperature suitable to vacuum pyrolize the support
material.
[0059] After the filament assembly is dried, the filament assembly
is removed from the frame and heated to bind the matrix material
with the inorganic binder and bond the plurality of sorbent
filaments to one another with the binding material, and thereby
form the sorbent substrate. In the embodiments of the sorbent
substrate described herein, the substrate is heated to a
temperature sufficient to bind the matrix material with the
inorganic binder contained in the matrix material and
simultaneously bind the individual filaments to one another. For
example, in embodiments where the inorganic binder is silica or a
silicone emulsion, the filament assembly may be heated to a
temperature T such that 250.degree. C..ltoreq.T.ltoreq.800.degree.
C. This temperature range is also suitable for binding the
filaments together with the binding material. In embodiments where
the inorganic binder is a silicone emulsion, the filament substrate
may be heated to and held at a temperature which is sufficient to
either partially or fully oxidize the silicone of the emulsion to
silica. For example, the filament assembly may be heated to a
temperature of in greater than about 500.degree. C., for example,
from about 500.degree. C. to about 700.degree. C., and held for
three hours to reduce substantially all of the silicone to silica
and thereby bind the sorbent material. Alternatively, the filament
assembly may be heated to a temperature of 250.degree. C. and held
for three hours to cross link the silicone and thereby bind the
sorbent material.
EXAMPLES
[0060] The methods for forming the sorbent substrate described
herein will be further clarified with reference to the following
example.
Example 1
[0061] A plasticized batch of matrix material was formed from CBF
3024E ZSM-5 zeolite manufactured by Zeolyst, M97E silicone emulsion
manufactured by Wacker-Chemie GmbH, Culminal 724 hydroxypropyl
methylcellulose binder manufactured by Hercules Incorporated,
Durasyn 162 lubricant manufactured by Ineos Group Ltd., tall oil
manufactured by MeadWestvaco, and deionized water. Specifically,
the zeolite and the hydroxypropyl methylcellulose binder were dry
mixed in a Nalgene container with a three-axis mixer. The remaining
components (i.e., the silicone emulsion, lubricant, tall oil and
deionized water) were blended into the dry powder mixture using a
wheel and plow muller to form an extrudable plasticized batch of
matrix material. The resultant batch comprised 56.8 wt. % zeolite
as the sorbent material, 34.1 wt. % silicone emulsion as the
inorganic binder, 3.4 wt. % hydroxypropyl methylcellulose as the
organic binder, 1.1 wt. % Durasyn 162 lubricant, 0.6 wt. % tall oil
lubricant, and 4.0 wt. % deionized water as the liquid vehicle.
[0062] A plasticized batch of support material was also formed from
Ultraflex micro crystalline wax manufactured by Bareco, tall oil
manufactured by MeadWestvaco and Micro 450 graphite lubricant
manufactured by Asbury Carbons. Specifically, the wax was melted
and mixed with the tall oil and the graphite was subsequently added
to the mixture. Thereafter the mixture was cooled and solidified.
The resultant plasticized batch of support material comprised 90.9
wt. % wax as the support material, 6.4 wt. % tall oil as a
lubricant and 2.7 wt. % graphite as a lubricant.
[0063] The plasticized batch of matrix material was extruded into
10 millimeter matrix rods and the plasticized batch of support
material was extruded into 10 millimeter channel rods. The matrix
rods and the channel rods were fed into the co-extrusion die
depicted in FIG. 3 with ram extruders to produce a plurality of 2
mm diameter sorbent filaments of circular cross section and having
seven 150 .mu.m diameter through-channels extending through the
filament in an axial direction filled with support material.
[0064] The plurality of sorbent filaments were coated with an
alumina slurry having a particle size of 70 .mu.m to form a 210
.mu.m thick alumina coating around each sorbent filament. The
sorbent filaments were then stacked and axially aligned in a
cylindrical, two-piece segmented frame and compressed with band
clamps wrapped around the cylindrical frame to form a circular
filament assembly having a diameter of 101.6 mm The filament
assembly was dried at a temperature of 90.degree. C. for 12 hours
in a convection oven while the assembly was inclined at an angle of
25 degrees to allow the support material to drain from the
through-channels.
[0065] Thereafter, the filament assembly was removed from the
segmented frame and heated to a temperature of 700.degree. C. and
held at that temperature for 3 hours to bind the adjacent sorbent
filaments together and to bind the matrix of sorbent material of
each sorbent filament, thereby creating a sorbent substrate having
a diameter of 101.6 mm, a length of 91 cm and comprising a
plurality of 150 .mu.m diameter through-channels.
[0066] Referring now to FIG. 6, the sorbent substrates described
herein may be used in a CO.sub.2 recovery unit such as the CO.sub.2
recovery unit depicted in FIG. 6. Specifically, the sorbent
substrates 100 are positioned in a pressure vessel 202 of the
CO.sub.2 recovery unit 200 which includes a process gas inlet 212,
a process gas outlet 214, a control fluid inlet 204 coupled to a
control fluid inlet manifold 208, and a control fluid outlet 206
coupled to a control fluid outlet manifold 210. The sorbent
substrates 100 are positioned in the interior of the pressure
vessel 202 and the through-channels 104 of the sorbent substrate
are fluidly coupled to the control fluid inlet manifold 208 at one
end of the substrate and to the control fluid outlet manifold 210
at the opposite end of the substrate.
[0067] In operation, CO.sub.2 can be removed from a process gas
stream 218 by coupling the process gas stream 218 into the CO.sub.2
recovery unit 200 through the process gas inlet 212. As the process
gas stream 218 permeates into and diffuses through the pores of the
sorbent substrates 100, the CO.sub.2 in the process gas stream 218
is adsorbed by the sorbent material and the process gas stream
exits the pressure vessel 202 through the process gas outlet 214 as
a CO.sub.2-free process gas stream 220. The adsorption of the
CO.sub.2 by the sorbent material produces heat. Accordingly, at the
same time the process gas flows through the pressure vessel 202, a
control fluid 216, specifically a cooling fluid such as nitrogen
gas or water, is introduced into the control fluid inlet 204 such
that the control fluid 216 flows through the control fluid inlet
manifold 208, into the through-channels 104 of the sorbent
substrates 100, and exits the CO.sub.2 recovery system through the
control fluid outlet manifold 210 and control fluid outlet 206,
thereby dissipating the heat produced by the adsorption of the
CO.sub.2 by the sorbent substrates 100.
[0068] Over time, the sorbent substrates 100 become saturated with
CO.sub.2 and require regeneration. To regenerate the sorbent
substrates, a control fluid 216, specifically a heated gas or vapor
such as steam, or a heated liquid such as water, is introduced into
the control fluid inlet 204 such that the control fluid 216 flows
through the control fluid inlet manifold 208, into the
through-channels 104 of the sorbent substrates 100, and exits the
CO.sub.2 recovery system through the control fluid outlet manifold
210 and control fluid outlet 206. The heated control fluid supplies
thermal energy to the sorbent substrates which causes the
desorption of the CO.sub.2 from the sorbent material of the sorbent
substrates. At the same time, a purge gas, such as nitrogen, is
introduced into the pressure vessel 202 through the process gas
inlet 212. The purge gas permeates into and diffuses through the
porous sorbent material of the sorbent substrates, flushing the
CO.sub.2 released from the sorbent material and carrying the
CO.sub.2 out of the pressure vessel 202 through the process gas
outlet 220.
[0069] Referring now to FIG. 7, the sorbent substrates described
herein may also be used in CO.sub.2 recovery units with alternate
configurations, such as the CO.sub.2 recovery unit 201 depicted in
FIG. 7. Specifically, sorbent substrates 100 with through-channels
104 and conduits 108 are positioned in a pressure vessel 202 of the
CO.sub.2 recovery unit 201. A process gas inlet manifold 240 and a
process gas outlet manifold 242 are fluidly coupled to the pressure
vessel 202 and to the through channels 104 of the sorbent
substrates 100 such that a process gas stream 218 flowing through
the process gas inlet manifold 240 passes through the
through-channels 104 and exits the CO.sub.2 recovery unit 201
through the process gas outlet manifold 242 as a CO.sub.2-free gas.
A control fluid inlet manifold 208 and a control fluid outlet
manifold 210 are fluidly coupled to the conduits 108 extending
through the sorbent substrates 100 but fluidly isolated from the
sorbent material and flow-through channels 104 of the sorbent
substrates 100. Control fluid 216 passing though the control fluid
inlet manifold 208 passes through the conduits and exits the
CO.sub.2 recovery unit 201 through the control fluid outlet
manifold 210.
[0070] In operation, CO.sub.2 can be removed from a process gas
stream 218 by coupling the process gas stream 218 into the CO.sub.2
recovery unit 201 through the process gas inlet manifold 240. As
the process gas stream 218 travels through the through-channels 104
of the sorbent substrate 100, the CO.sub.2 in the process gas
stream 218 is adsorbed by the sorbent material and the process gas
stream exits the pressure vessel 202 through the process gas outlet
manifold 242 as a CO.sub.2-free process gas stream 220. The
adsorption of the CO.sub.2 by the sorbent material produces heat.
Accordingly, at the same time the process gas flows through the
pressure vessel 202, a control fluid 216, specifically a cooling
fluid such as nitrogen gas or water, is introduced into the control
fluid inlet manifold 208, passes through the conduits 108, and
exits the CO.sub.2 recovery system through the control fluid outlet
manifold 210 thereby dissipating the heat produced by the
adsorption of the CO.sub.2 by the sorbent substrates 100.
[0071] Over time, the sorbent substrates 100 become saturated with
CO.sub.2 and require regeneration. To regenerate the sorbent
substrates, a control fluid 216, specifically a heated gas or vapor
such as steam, or a heated liquid such as water, is introduced into
the control fluid inlet manifold 208, into the through-channels 104
of the sorbent substrates 100, and exits the CO.sub.2 recovery
system through the control fluid outlet manifold 210. The heated
control fluid supplies thermal energy to the sorbent substrates
which causes the desorption of the CO.sub.2 from the sorbent
material of the sorbent substrates. At the same time, a purge gas,
such as nitrogen, is introduced into the pressure vessel 202
through the process gas inlet manifold 240. The purge gas flushes
the CO.sub.2 released from the sorbent material out of the sorbent
substrates 100 thereby carrying the CO.sub.2 out of the pressure
vessel 202 through the process gas outlet manifold 242.
[0072] It should now be understood that the methods described
herein may be utilized to form a sorbent substrate from a plurality
of sorbent filaments such that the sorbent substrate is suitable
for use in removing CO.sub.2 from a process gas stream.
Specifically, forming the individual sorbent filaments by
co-extruding sorbent material with a support material facilitates
forming each of the sorbent filaments with a plurality of
through-channels without the through-channels collapsing during the
extrusion process or during subsequent assembly of the sorbent
substrate. As a result, the sorbent substrates constructed from the
sorbent filaments have a high density of through-channels, which
may be used to efficiently cool the sorbent substrate as CO.sub.2
is adsorbed by the sorbent material of the sorbent filaments and to
efficiently heat the sorbent substrate during subsequent
regeneration of the sorbent substrate to remove the CO.sub.2
captured in the sorbent material of the substrate.
[0073] In a first aspect, the disclosure provides a method for
forming a sorbent substrate (100) for CO.sub.2 capture, the method
comprising: forming a plurality of matrix rods from a sorbent
material (106) for adsorbing CO.sub.2 from a gas stream; forming a
plurality of channel rods from a support material; co-extruding the
plurality of matrix rods with the plurality of channel rods to form
a plurality of sorbent filaments (102) comprising a matrix of the
sorbent material (106) comprising channels (104) of support
material (110), the channels (104) of support material (110)
extending in an axial direction of each of the plurality of sorbent
filaments (102); stacking the plurality of sorbent filaments (102)
to form a filament assembly, wherein the plurality of sorbent
filaments (102) are axially aligned in the filament assembly; and
bonding the plurality of sorbent filaments (102) of the filament
assembly to one another to form the sorbent substrate (100).
[0074] In a second aspect, the disclosure provides a method for
forming a sorbent substrate (100) for CO.sub.2 capture, the method
comprising: forming a plasticized batch of matrix material
comprising a sorbent material (106) for adsorbing CO.sub.2 from a
process gas stream; forming a plasticized batch of fugitive
material; co-extruding the plasticized batch of matrix material
with the plasticized batch of fugitive material to form a plurality
of sorbent filaments (102) comprising a matrix of the sorbent
material (106) having channels (104) of fugitive material extending
in an axial direction of each of the plurality of sorbent filaments
(102); stacking the plurality of sorbent filaments (102) to form a
filament assembly, wherein the plurality of sorbent filaments (102)
are axially aligned in the filament assembly; compressing the
filament assembly; removing the fugitive material from the filament
assembly to form a plurality of through-channels (104) in each of
the plurality of sorbent filaments (102); and heating the filament
assembly to bond the plurality of sorbent filaments (102) to one
another to form the sorbent substrate (100).
[0075] In a third aspect, the disclosure provides the method of the
first aspect, wherein the support material (110) is a fugitive
material; and the method further comprises removing the fugitive
material from the plurality of sorbent filaments (102) thereby
forming through-channels (104) in the plurality of sorbent
filaments (102).
[0076] In a fourth aspect, the disclosure provides the method of
any of any of the first through third aspects, further comprising
coating the plurality of sorbent filaments (102) with a binding
material prior to stacking the plurality of sorbent filaments (102)
to form the filament assembly.
[0077] In a fifth aspect, the disclosure provides the method of the
fourth aspect, wherein the binding material comprises a slurry of
alumina powder.
[0078] In a sixth aspect, the disclosure provides the method of any
of the first aspect or the third through fifth aspects, further
comprising radially compacting the filament assembly.
[0079] In a seventh aspect, the disclosure provides the method of
any of the first aspect and the third through sixth aspects,
wherein the plurality of sorbent filaments (102) are bonded to one
another by heating the filament assembly.
[0080] In an eighth aspect, the disclosure provides the method of
the seventh aspect, wherein the filament assembly is heated to a
temperature T in a range such that 250.degree.
C..ltoreq.T.ltoreq.850.degree. C.
[0081] In a ninth aspect, the disclosure provides the method of any
of the first through eighth aspects, wherein the matrix of the
sorbent material (106) has a first porosity P1% such that
20%.ltoreq.P1%.ltoreq.70%.
[0082] In a tenth aspect, the disclosure provides the method of any
of the first through ninth aspects, wherein the sorbent substrate
(100) has a voidage V such that 25%.ltoreq.V.ltoreq.75%.
[0083] In an eleventh aspect, the disclosure provides the method of
any of the first through tenth aspects, further comprising stacking
one or more conduits (108) with the plurality of sorbent filaments
(102) to form the filament assembly.
[0084] In a twelfth aspect, the disclosure provides the method of
any of the first through eleventh aspects, further comprising
drying the filament assembly prior to bonding the plurality of
sorbent filaments (102) to one another.
[0085] In a thirteenth aspect, the disclosure provides the method
of the twelfth aspect, wherein the filament assembly is dried by
heating the filament assembly to a drying temperature T.sub.d,
wherein 90.degree. C..ltoreq.T.sub.d.ltoreq.150.degree. C.
[0086] In a fourteenth aspect, the disclosure provides the method
of any of the first through tenth aspects and the twelfth through
thirteenth aspects, further comprising positioning at least one
conduit (108) amongst the plurality of sorbent filaments (102) as
the plurality of sorbent filaments (102) are stacked, wherein the
at least one conduit (108) is formed from a material other than the
sorbent material (106).
[0087] In a fifteenth aspect, the disclosure provides the method of
any of the second through fourteenth aspects, wherein the
plasticized batch of matrix material comprises from about 30 wt. %
to about 75 wt. % of sorbent material (106); from about 20 wt. % to
about 40 wt. % of inorganic binder; and from about 1 wt. % to about
10 wt. % organic binder.
[0088] In a sixteenth aspect, the disclosure provides the method of
any of the first through fifteenth aspects, wherein each of the
plurality of through-channels (104) has a diameter d such that 20
.mu.m.ltoreq.d.ltoreq.2000 .mu.m.
[0089] In a seventeenth aspect, the disclosure provides a sorbent
substrate (100) for CO.sub.2 capture, the sorbent substrate (100)
comprising: a plurality of sorbent filaments (102), each sorbent
filament (102) of the plurality of sorbent filaments (102)
comprising a matrix of sorbent material (106) in which a plurality
of through-channels (104) are formed such that the plurality of
through-channels (104) extend through the matrix of sorbent
material (106) from a first end of each sorbent filament (102) to a
second end of each sorbent filament (102) in an axial direction of
each sorbent filament (102), wherein: the sorbent material (106) is
capable of adsorbing CO.sub.2 from a gas stream; the plurality of
sorbent filaments (102) are axially aligned with one another such
that the plurality of through-channels (104) of the plurality of
sorbent filaments (102) are substantially parallel with one
another; and each sorbent filament (102) of the plurality of
sorbent filaments (102) is bonded to at least one other sorbent
filament.
[0090] In an eighteenth aspect, the disclosure provides a sorbent
substrate (100) of the seventeenth aspect, further comprising at
least one conduit (108) axially aligned with the plurality of
sorbent filaments (102), wherein the at least one conduit (108) is
formed from a material other than the sorbent material (106).
[0091] In nineteenth aspect, the disclosure provides a sorbent
substrate (100) of any of the seventeenth aspect or the eighteenth
aspect, wherein the sorbent substrate (100) has a porosity P1% such
that 20%.ltoreq.P1%.ltoreq.70%.
[0092] In a twentieth aspect, the disclosure provides a sorbent
substrate (100) of any of the seventeenth through nineteenth
aspects, wherein the sorbent substrate (100) has a voidage V such
that 25%.ltoreq.V.ltoreq.75%.
[0093] It will be apparent to those skilled in the art that various
modifications and variations can be made to the embodiments
described herein without departing from the spirit and scope of the
claimed subject matter. Thus, it is intended that the specification
cover the modifications and variations of the various embodiments
described herein provided such modification and variations come
within the scope of the appended claims and their equivalents.
* * * * *